Most conventional coating resins are insoluble in water. Therefore, in general practice they have been dissolved in a suitable organic solvent or dispersed in water with the aid of an emulsifying agent or surfactant in order to provide a coating composition suitable for application to a substrate surface. A serious disadvantage of organic solvent solutions is that they are potentially toxic, flammable, and environmental pollutants.
Water reducible coatings do not present these problems and are, therefore, highly desirable. For this reason various water reducible coating resins, such as the one described in U.S. Pat. No. 4,474,926, have been developed. Water reducible coatings which utilize such resins have been developed for a variety of purposes, such as highway striping paint.
Conventional thickening agents which are used in organic solvent based coatings do not normally act as thickening agents in aqueous coating systems. Nevertheless, there is a need for thickening agents which can be used in aqueous coating systems. The present invention relates to the development of a thickening agent for use in aqueous coating systems which has thixotropic properties.